Level A represents the producers which make their own food and are mainly comprised of the plants of our world. They gain energy from the sun and through the process of photosynthesis.
The energy for use by organisms in level A originally comes from sun. Thus the correct option is A.
What is photosynthesis?
The process through which green plants and some other organisms use sunlight to make foods from carbon dioxide and water. Photosynthesis in plants generally involves the green colour pigment chlorophyll and generates oxygen as a byproduct.
Whereas, B would be primary consumers which are the herbivores, C are the secondary consumers that include omnivorous, and D are the decomposers, which include worms.
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